The present invention relates to a technology for contriving higher output and higher efficiency and enhancing image quality and the like in a one-dimensional illumination apparatus and an imaging apparatus which use a one-dimensional transverse multiple mode laser.
Solid state lasers are used in the cases where a high output is desirable. In the cases of using a semiconductor laser as a pumping light source, there have been known, for example, a form in which a laser array having a plurality of emitters (radiation sources) and an optical device (micro-lens array) are combined (see, for example, Japanese Patent Laid-open No. 2001-185792), and a form in which a diode array and a collimation cylindrical lens are combined (see, for example, U.S. Pat. No. 5,521,932).
In addition, nonlinear optical crystals are used for wavelength conversion and the like. For example, in the case of second harmonic generation (SHG), green light can be obtained by incidence of near IR external light. In the case of an optical waveguide circuit type device, a device having a periodical poling structure along the direction of an optical waveguide circuit has been known, which can be mass-produced at a lower cost by the wafer process technology.
In application to imaging apparatuses (projectors, printers, etc.) using a laser light source and a light modulation device, a configuration in which an image display light modulation device having a one-dimensional spatial modulation type structure has been known for enhancing the resolution of image. For example, in application to image projectors, by providing a light modulation device for modulating the light from a laser light source and projecting an image onto a screen by light scanning of the flux from the light modulation device, it is possible to project a two-dimensional image.
However, the configurations according to the related art have problems as to the output and efficiency of the laser light source and the like.
For example, in application to image projectors and the like, it is desirable to use a green laser apparatus with an output of about 5 W, but it is difficult to actually produce a high-output high-efficiency laser, or the use of an expensive apparatus leads to such problems as a rise in cost. In addition, in order to form a line beam with which to irradiate a one-dimensional light modulation device from a spot-like laser light, it is desirable to use a profile conversion optical system, a line generator or the like, which causes complication of configuration. Besides, it may be necessary to perform an optical adjustment (alignment) with high accuracy, or the number of portions to be adjusted may be increased, resulting in an influence on stability or the like problems.
In addition, a measure to reduce the speckle noise arising from the high coherence of a laser light may be required in application to laser displays or the like.
Besides, where non-uniformity in beam intensity of one-dimensional oscillation is observed, irregularities in intensity may be generated at the time of illumination. Therefore, where transverse pumping of a laser medium is performed in the configuration of a solid state laser, uniformity of the pumping light in the transverse direction may matter.